Balanced piston



(No Model.

W. J. THOMAS.

BALANGED PISTON.

No. 473,032. Patented Apr. 19, 1892.

Wifnes5es: I: InUenTur v wm P M UNITED STATES PATENT OFFICE.

WILLIAM J. THOMAS, OF SAUSALITO, ASSIGNOR OF ONE-HALF TO JOHN T. WILSON,OF SAN FRANCISCO, CALIFORNIA.

BALANCED PISTON.

SPECIFICATION forming part Of Letters Patent No. 473,032, dated April19, 1892.

Application filed June 17, 1891. Serial No. 396,620. (No model.) I

To all whom it may concern.-

Be it known that 1, WILLIAM J. THOMAS, a citizen of the United States,residing in Sausalito, in the county of Marin and State of California,have invented certain new and useful Improvements in Balanced Pistonsfor Steam-Engines, of which the followingis a specification.

This invention relates to that improvement in balancing-pistons forwhich Letters Patent of the United States were issued to me on the 11thday of June, 1889,'No. 405,132; and it embraces improvements in theconstruction of the packing-rings and in the arrangementof steam portsand passages in the piston.

The object of these improvements is to simplify the construction of theparts and to insure a better supply and perfect control of thesteam-pressure by which the balancing is effected.

I proceed to attain the desired ends and object and produce theseimprovements by the construction and arrangement of parts represented inthe accompanying drawings, in which Figure 1 is a side elevation of abalanced piston to which myimprovements are applied, the top and bottomportions of the surrounding cylinder being shown in section. Fig. 2 is alongitudinal section through the piston in a vertical plane. Fig. 3 isatop View of the piston. Figs. 4 and 5 illustrate the manner of formingthe lap and joint of the packingring. Fig. 6 shows the finished-ring.

, X Y indicate the top and bottom sides of the cylinder.

A is the piston, and BB are the packingrings.

O is the steam-chamber or hollow space in the piston, and D E are portsand passages opening into the space Q through the piston.

' The packing-rings are set obliquely, the same as in my former patent,No. 405,132; but the passage D is carried from the outside into thesteam-space 0 through that part of the face or rim of the piston whichlies between the two rings at or near the top side of the piston ,wherethe two packing-rings approach the nearest to each other. This inlet iscom mon to the two packing-rings and steam is admitted through it intothe piston-chamber C from one groove or the other, according to thedirection of the travel of the piston-that is, from the pressure side ofthe piston.

The packing-rings are fitted loosely in the piston-grooves and the steamfrom the pressure side passes around the leading or foremost ring and sointo the space between the two rings where the inlet D is located.

The general action oroperationof therings is the same as in my formerpatent. The packing-rings have sufficient I play in the grooves to letthe steam from the pressure side pass into the space 0, and in beingshifted by the movement of the piston from one side of its groove to theother the leading ring admits steam, while the other ring, which isbetween the exhaust side of the piston and the steam-inlet, is pressedcloselyagainstthe outer side of its groove to shut off the inlet D andthe space 0 from the exhaust. The two rings thus act alternately uponthe steam inlet, which is common to both, and a more regular and uniformdegree of pressure is maintained in the space beneath the piston betweenthe two rings and the bottom of the cylinder on which the pistontravels. The inlet D serves to give quick inlet of steam directly to thespace under the piston; but in addition to that supply it will benoticed that the steampressure after passing the joint of the ring intothe space between the two rings is free to pass around the circumferenceof the piston itself and then find its Way into the space under thepiston and a larger volume of steam is obtained to raise the piston fromthe cylinder through these passages. The admission and supply is moredirect and quick, however, through the ports D E and the space insidethe piston.

The joints of the packing-rings areconstructed to give a suitable spaceand passage for the steam both between the ring and the bottom of thegroove and on the inner side when the steam-pressure is against theouter side of the ring; but the outside face of the ring is flush andforms a joint that is closed to the steampressure when the outside faceof the ring is seated against the side of the groove. The joint l3 istherefore flush or continuous on the outer side as well as on the top orworking face, while it is cut away or broken on the bottom and on theinner side. It is also expansible to accommodate itself to the elas-'ticity of the ring. In constructing or forming this joint the ring isfirst finished 011 the sides and top face, and the parts for the jointare formed, as shown in Figs. at and 5, by cutting or milling them outof the solid metal. The portion from 1 to 2 is cut away on the inner orbottom face, the portion from 3 to 4: is cut away across the ring on theouter side,

and the part from 5 to 6 is formed on the inner face for about one-halfthe thickness of the metal, the portion of metal from 1 to 2 being cutaway. to a corresponding amount on the opposite face. After theseoperations the ring is separated at the line 00 y across the milled andcut-away port-ions,and the lap is produced by passing the two endportions for about one-third the circumference be tween rollers, whichare placed in relative position, as indicated by the dotted lines, Fig.6. By this means not only a close expansible joint is obtained, but thering when finished and sprung into place will be cylindrical.

Snap-rings with lap-joints under all other modes of construction willnot be true circles, and therefore not so well adapted for my purpose.

To illustrate the action of the steam in the piston, suppose thepressure to be on the right of the piston, as shown in Figs. 1, 2, and3, the right-hand ring B will be forced against the inner edge of thegroove in the piston and a space or passage for the steam will beprovided between the ring and the outer edge of the groove, as seen inFig. 3, thence under the cut-away portion 1 to 2, and out throughcut-away portion 3 to 4 (see Figs. 5 and 6) into the space between therings. The ring B on the left of the piston will at the same time make atight joint all round against the outer edge of the piston-groove byreason of the continuous unbroken contact of the ring with the saidouter edge, as may be seen in Fig. 3, and as will beclearly indicated bythe side elevation of the ring, (shown in Fig. 6,) and no steam cantherefore pass this left-hand ring when the pressure is uponthe right ofthe piston. When the pressure is shifted to the left of the piston, thecondition of the rings will be reversed, as will be readily understood.

Having thus fully described my invention,

what I claim, and desire to secure by Letters Patent, is

- 1. In a balanced piston for steam-engines, a piston havingobliquely-set packing-ring grooves, a steam space or chamber, andpassages communicating withthe outside through the opposite faces of thepiston and between the said grooves, in combination with packing-ringsprojecting beyond the peripheryof the piston-body, having lapping ends,with flush outer faces and cut-away portions onthe bottom and attheinner sides, constructed and arranged for operation substantially asset forth. v

2. In a balanced piston for steam-engines, having a piston withobliquely-set packing- :ring grooves, a packing-ring projecting beyondthe periphery of the piston-body and having a lap-joint with a tongue orreduced end portion, which is cut away on the bottom of the rings and onthe inner face, and a recessed end adapted to take the said tongue andform a lap-joint, as described.

' 3. In a balance-piston, the combination, with the hollow body of thepiston having peripheral openings and annular circumferential grooves,as described, of a pair of packing-rings each having a lap-joint, saidrings being of less width than the width of the grooves and eachlap-joint being formed of one recessed end and one reduced end of thering, said reduced end lying in said recess and making a tight joint allround in the groove When pressed against its outer edge, as set forth.

In testimony that I claim the foregoing I have hereunto set my hand andseal.

WVILLIAM J THOMAS. Witnesses:

JAMES L. KING, EDWARD E. OSBORN.

